﻿using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;


/*********************************************************
 * 
 * programmer:		patrick.woolhoo@gmail.com
 * svn:				http://woolhoo-net.googlecode.com/svn/trunk/wnet/
 * class:			SymmetricMethod
 * desc:			对称加密算法
 * 
 * *******************************************************/

namespace Patrick.Custom {

	/// <summary>  
	/// 对称加密算法类  
	/// </summary>  
	public class SymmetricMethod {

		private SymmetricAlgorithm mobjCryptoService;
		private string Key;
		/// <summary>  
		/// 对称加密类的构造函数  
		/// </summary>  
		public SymmetricMethod() {
			mobjCryptoService = new RijndaelManaged();
			Key = "hp training course system, written by:patrick.woolhoo@gmail.com";
		}
		/// <summary>  
		/// 获得密钥  
		/// </summary>  
		/// <returns>密钥</returns>  
		private byte[] GetLegalKey() {
			string sTemp = Key;
			mobjCryptoService.GenerateKey();
			byte[] bytTemp = mobjCryptoService.Key;
			int KeyLength = bytTemp.Length;
			if (sTemp.Length > KeyLength)
				sTemp = sTemp.Substring(0, KeyLength);
			else if (sTemp.Length < KeyLength)
				sTemp = sTemp.PadRight(KeyLength, ' ');
			return ASCIIEncoding.ASCII.GetBytes(sTemp);
		}
		/// <summary>  
		/// 获得初始向量IV  
		/// </summary>  
		/// <returns>初试向量IV</returns>  
		private byte[] GetLegalIV() {
			string sTemp = "E4ghj*Ghg7!rNIfb&95GUY86GfghUb#er57HBh(u%g6HJ($jhWk7&!hg4ui%$hjk";
			mobjCryptoService.GenerateIV();
			byte[] bytTemp = mobjCryptoService.IV;
			int IVLength = bytTemp.Length;
			if (sTemp.Length > IVLength)
				sTemp = sTemp.Substring(0, IVLength);
			else if (sTemp.Length < IVLength)
				sTemp = sTemp.PadRight(IVLength, ' ');
			return ASCIIEncoding.ASCII.GetBytes(sTemp);
		}
		/// <summary>  
		/// 加密方法  
		/// </summary>  
		/// <param name="Source">待加密的串</param>  
		/// <returns>经过加密的串</returns>  
		public string Encrypto(string Source) {
			byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
			MemoryStream ms = new MemoryStream();
			mobjCryptoService.Key = GetLegalKey();
			mobjCryptoService.IV = GetLegalIV();
			ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
			CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
			cs.Write(bytIn, 0, bytIn.Length);
			cs.FlushFinalBlock();
			ms.Close();
			byte[] bytOut = ms.ToArray();
			return Convert.ToBase64String(bytOut);
		}
		/// <summary>  
		/// 解密方法  
		/// </summary>  
		/// <param name="Source">待解密的串</param>  
		/// <returns>经过解密的串</returns>  
		public string Decrypto(string Source) {
			byte[] bytIn = Convert.FromBase64String(Source);
			MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
			mobjCryptoService.Key = GetLegalKey();
			mobjCryptoService.IV = GetLegalIV();
			ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
			CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
			StreamReader sr = new StreamReader(cs);
			return sr.ReadToEnd();
		}
	}
}